New evidence shows that polar bears are suffering from industrial chemicals swept to the Arctic from nations thousands of kilometres to the south, conservationists say.

The WWF global conservation organisation called for a wider ban on the toxic chemicals, including some in a newer generation meant to be less harmful than a 'dirty dozen' outlawed by a 2001 convention.

"Three new scientific studies published recently provide strong indications that polar bears are contaminated by PCBs [polychlorinated biphenyls] and pesticides, and are already being affected by these chemicals," it said in a report.

The WWF said that it was calling for "the immediate phase out of the most hazardous chemicals", saying the studies added to evidence of contamination of the Arctic by chemicals swept north by winds and currents from nations to the south.

An estimated 22,000 polar bears live in the Arctic and face other threats from climate change and loss of habitat.

PCBs and some pesticides were banned under the 2001 UN convention. They can linger for years in the environment and build up in animals' fatty tissues. Some studies have shown traces of newer chemicals, including types of flame retardants.

The WWF said the three studies indicated a link between high levels of PCBs and pesticides in polar bears in Canada and on the Norwegian island of Svalbard and a lack of antibodies in their blood, making the bears more susceptible to infection.

The studies also found altered hormone levels that could lead to reproductive and behaviour problems.

"Most polar bears probably have several hundred man-made chemicals in their bodies and they have never evolved mechanisms to deal with them," said Professor Andrew Derocher, a Canadian scientist at the University of Alberta who has contributed to the recent studies.

"The unintentional tinkering with the hormone and immune system of a polar bear is unlikely to be good for them."

Polar bears, whose favourite diet is fatty seals, often have high levels of contaminants which have also been found, for instance, in the breast milk of Inuit women.